Electronics tester

ABSTRACT

A tester apparatus is described. Various components contribute to the functionality of the tester apparatus, including an insertion and removal apparatus, thermal posts, independent gimbaling, the inclusion of a photo detector, a combination of thermal control methods, a detect circuitry in a socket lid, through posts with stand-offs, and a voltage retargeting.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority from U.S. Provisional PatentApplication No. 62/466,462, filed on Mar. 3, 2017 and U.S. ProvisionalPatent Application No. 62/526,089, filed on Jun. 28, 2017, which arehereby incorporated by reference into the present application in theirentirety.

BACKGROUND OF THE INVENTION 1). Field of the Invention

This invention relates to a tester apparatus that is used for testingmicroelectronic circuits.

2). Discussion of Related Art

Microelectronic circuits are usually fabricated in and on semiconductorwafers. Such a wafer is subsequently “singulated” or “diced” intoindividual dies. Such a die is typically mounted to a supportingsubstrate for purposes of providing rigidity thereto and for electroniccommunication with an integrated or microelectronic circuit of the die.Final packaging may include encapsulation of the die and the resultingpackage can then be shipped to a customer.

It is required that the die or the package be tested before beingshipped to the customer. Ideally, the die should be tested at an earlystage for purposes of identifying defects that occur during early stagemanufacture. Wafer level testing may be accomplished by providing ahandler and a contactor with contacts and then using the handler to movethe wafer so that contacts on the wafer make contact with the contactson the contactor. Power and electronic signals can then be providedthrough the contactor to and from microelectronic circuits formed in thewafer.

According to various embodiments a wafer includes a substrate such as asilicon substrate or a printed circuit board and one or more devicesfabricated in the substrate or mounted to the substrate.

Alternatively, the wafer can be located within a portable cartridgehaving an electrical interface and a thermal chuck. Power and signalscan be provided through the electric interface to and from the waferwhile a temperature of the wafer is thermally controlled by heating orcooling the thermal chuck.

After the wafer is singulated it may again be required to test theindividual dies, and it may again be required to test the die after itis mounted to a supporting substrate.

SUMMARY OF THE INVENTION

The invention provides a testing apparatus including a frame, a slotassembly on the frame, a slot assembly interface on the slot assembly, aholding structure to place a cartridge holding a plurality ofmicroelectronic devices, a horizontal transportation apparatus operableto move the cartridge horizontally from a first position to a secondposition into the slot assembly, a vertical transportation apparatusoperable to move the cartridge and the slot assembly in a first verticaldirection relative to one another to engage the slot assembly interfacewith a cartridge interface on the cartridge and a tester connectedthrough the first slot assembly interface and the cartridge interface toprovide at least power to each microelectronic device and to measure aperformance of the microelectronic device, the vertical transportationapparatus being operable to move the cartridge and the slot assembly ina second vertical direction relative to one another, the second verticaldirection being opposite to the first vertical direction to disengagethe slot assembly interface from the cartridge interface, and thehorizontal transportation apparatus being operable to move the cartridgehorizontally from the second position to the first position out of theslot assembly.

The invention also provides a method of testing electronic devicesincluding holding a cartridge holding a plurality of microelectronicdevices in a first position at least partially outside a slot assemblyon a frame, moving the cartridge horizontally from the first position toa second position into a slot assembly, moving the cartridge and theslot assembly in a first vertical direction relative to one another toengage a slot assembly interface on the slot assembly with a cartridgeinterface on the cartridge, testing the microelectronic devices throughthe first slot assembly interface and the cartridge interface byproviding at least power to each microelectronic device and measuring aperformance of the microelectronic device, moving the cartridge and theslot assembly in a second vertical direction relative to one another,the second vertical direction being opposite to the first verticaldirection to disengage the slot assembly interface from the cartridgeinterface and moving the cartridge horizontally from the second positionto the first position out of the slot assembly.

The invention further provides a cartridge including a socket made ofinsulative material and having upper and lower sides, the upper sidehaving a first formation for releasably holding a first electronicdevice, the socket having a first socket thermal opening formed from thelower side to the upper side through the socket, an interface connectedto the socket to connect the first device to an electric tester, a chuckof a thermally conductive material and a first thermal post attached tothe chuck, the first thermal post being inserted into the first socketthermal opening, an end of the first thermal post being thermallyconnected to the first device, such that heat transfers primarilythrough the first thermal post as opposed to the insulative material ofthe socket between the chuck and the first electronic device.

The invention also provides a test piece including a socket made ofinsulative material and having upper and lower sides, the upper sidehaving a first formation for releasably holding a first electronicdevice, the socket having a first socket thermal opening formed from thelower side to the upper side through the socket, a first thermallyconductive post being insertable from the lower side into the firstsocket thermal opening, a first set of pins held in the socket andconnecting the first device to the circuit board, the first set of pinsbeing resiliently depressible and a lid that is movable relative to thesocket to depress the first set of pins to bring the first electronicdevice into contact with the end of the first thermal post.

The invention further provides a test piece including a chuck of athermally conductive material and a first thermal post attached to thechuck, the first thermal post being insertable into a first socketthermal opening with an end of the first thermal post being thermallyconnected to the first device, such that heat transfers primarilythrough the first thermal post as opposed to an insulative material ofthe socket between the chuck and the first electronic device.

The invention also provides a method of testing one or more electronicdevices including releasably holding a first device a first formation ofan upper side of a socket made of insulative material, connecting thefirst device to an electric tester through an interface connected to thesocket, inserting a first thermal post attached to a chuck of thermallyconductive material into a first socket thermal opening formed from alower side to the upper side through the socket, an end of the firstthermal post being thermally connected to the first device andtransferring heat between the chuck and the first electronic device, theheat transferring primarily through the first thermal post as opposed tothe insulative material of the socket.

The invention further provides a cartridge including a socket ofinsulative material and having upper and lower sides, a first formationon the upper side to hold a first electronic device, and a secondformation on the upper side to hold a second electronic device, a lid, afirst pusher plate rotatably mounted to the lid, a second pusher platerotatably mounted to the lid, the lid being locatable over the socketand movable towards the socket, the rotatable mounting of the firstpusher plate allowing for the first electronic device to rotate thefirst pusher plate relative to the lid and the rotatable mounting of thesecond pusher plate allowing the second electronic device to rotate thesecond pusher plate independently from the first pusher plate relativeto the lid, a first set of contacts held in the socket to connect to thefirst electronic device, a first set of terminals connected to the firstset of contacts, a second set of contacts held in the socket to connectto the second electronic device and a second set of terminals connectedto the second set of contacts.

The invention also provides a method of testing one or more electronicdevices including releasably holding a first electronic device in afirst formation on an upper side of a socket of insulative material,releasably holding a second electronic device in a second formation onan upper side of a socket, locating a lid over the socket, the lidhaving a first pusher plate rotatably mounted to the lid and a secondpusher plate rotatably mounted to the lid, moving the lid towards thesocket, the rotatable mounting of the first pusher plate allowing forthe first electronic device to rotate the first pusher plate relative tothe lid and the rotatable mounting of the second pusher plate allowingthe second electronic device to rotate the second pusher plateindependently from the first pusher plate relative to the lid; andconnecting the first and second electronic devices to an electric testerthrough an interface connected to the socket.

The invention further provides a cartridge including an electronicdevice holder having a formation for removably holding an electronicdevice having an input contact and a light emitter, an input contact onthe electronic device holder to connect to the input contact on theelectronic device to provide an input electric power through the inputcontact on the electronic device holder to the input contact on theelectronic device, the input electric power causing the light emitter totransmit light, a light detector mounted to the electronic device holderand positioned to detect the light and generate an output electric powerin response to a magnitude of the light and an output contact connectedto the light detector to measure the output electric power.

The invention also provides a method of testing one or more electronicdevices including inserting an electronic device having an input contactand a light emitter into a device holder, connecting an input contact onthe electronic device holder to the input contact on the electronicdevice, providing an input electric power through the input contact onthe electronic device holder to the input contact on the electronicdevice, the input electric power causing the light emitter to transmitlight, detecting the light, transforming the light that is detected toan output electric power, measuring the output electric power through anoutput contact and removing the electronic device from the electronicdevice holder.

The invention further provides a testing apparatus including a sockethaving a formation for removably holding an electronic device having aninput terminal and a light emitter, an input contact on the socket toconnect to the input terminal on the electronic device to provide aninput electric power through the input contact on the socket to theinput terminal on the electronic device, the input electric powercausing the light emitter to transmit light, a temperature modificationdevice on a first side of the socket, which, when operated changestemperature to cause a temperature differential between the temperaturemodification device and the electronic device and a transfer of heatbetween the temperature modification device and the electronic device tomodify a temperature of the electronic device, a heat sink on a side ofthe socket opposing the temperature modification device, the heat sinkhaving a surface for absorbing the light, absorption of the lightcreating heat in the heat sink and a heat dissipation device thermallyconnected to the heat sink to remove the heat from the heat sink.

The invention also provides a method of testing one or more electronicdevices including inserting an electronic device having an input contactand a light emitter into a socket, connecting an input contact on thesocket to the input terminal on the electronic device, providing aninput electric power through the input contact on the socket to theinput terminal on the electronic device, the input electric powercausing the light emitter to transmit light, changing a temperature of atemperature modification device on a first side of the socket to cause atemperature differential between the temperature modification device andthe electronic device and a transfer of heat between the temperaturemodification device and the electronic device to modify a temperature ofthe electronic device, absorbing the light with a surface of a heat sinkon a side of the socket opposing the temperature modification device,the absorption of the light creating heat in the heat sink, removing theheat from the heat sink with a heat dissipation device thermallyconnected to the heat sink; and removing the electronic device from thesocket.

The invention further provides a cartridge including a socket ofinsulative material and having upper and lower sides and a formation onthe upper side to hold an electronic device, a set of contacts held inthe socket to connect to the electronic device, a set of terminalsconnected to the set of contacts held by the socket, a circuit board,the set of terminals connected to the set of contacts being connected toa set of contacts on the circuit board, a lid, a detector mounted to thelid, the lid being movable to be positioned over the socket with thedetector located in a position to detect a feature of the electronicdevice when and due to power being supplied through at least one of theset of terminals held by the socket to the electronic device and ameasurement channel connecting the detector to an interface on thecircuit board.

The invention also provides a method of testing one or more electronicdevices including releasably holding an electronic device in a socket ofinsulative material and having upper and lower sides and a formation onthe upper side to hold an electronic device, connecting a set ofcontacts held in the socket to the electronic device, connecting a setof terminals connected to the set of contacts to a set of contacts on acircuit board, moving a lid having a detector mounted thereto over thesocket, connecting the detector through a measurement channel to aninterface on the circuit board, supplying power through at least one ofthe contacts held by the socket to the electronic device, detecting afeature of the electronic device when and due to power being suppliedthrough at least one of the contacts held by the socket to theelectronic device and measuring the feature through the interface.

The invention further provides a cartridge including a supporting boardhaving a post opening therethrough, a backing structure, on a first sideof the supporting board, and including at least a circuit board having acontact, a conductor having a contact to make contact with a terminal onan electronic device positioned on a second side of the supporting boardopposing the first side of the supporting board, a portion held by thesupporting board and a terminal connected to the contact on the circuitboard, a spring, a force generation device on a side of the electronicdevice opposing the supporting board, the force generation device andthe supporting board being movable relative to one another to move theelectronic device closer to the supporting board and deform the springand a post having a stand-off with a surface in a plane spaced from aplane of a surface of the supporting board to prevent movement of theelectronic device closer to the supporting board, a force transferportion extending from the stand-off at least partially through the postopening, and a force delivery portion extending from the force transferportion, the force delivery portion being held by the backing structure.

The invention also provides a cartridge including positioning a backingstructure, including at least a circuit board having a contact, on afirst side of a supporting board, connecting a contact of a conductor toa terminal on and electronic device positioned on a second side of thesupporting board opposing the first side of the supporting board, theconductor having a portion held by the supporting board and a terminalconnected to the contact on the circuit board, positioning a forcegeneration device on a side of the electronic device opposing thesupporting board, moving the force generation device and the supportingboard being relative to one another to move the electronic device closerto the supporting board and deform a spring against a spring forcethereof, preventing movement of the electronic device closer to thesupporting board with a post having a stand-off with a surface in aplane spaced from a plane of a surface of the supporting board,receiving with the stand-off of a post a force from the electronicdevice, transferring the force from the stand-off at least partiallythrough the opening with a force transfer portion of the post extendingfrom the stand-off at least partially through a post opening formedthrough the supporting board, receiving the force with a force deliveryportion of the post extending from the force transfer portion, the forcedelivery portion being held by the backing structure and delivering theforce to the backing structure.

A tester apparatus including a voltage targeting system, a holder forholding a plurality of electronic devices in at least first and secondclusters, at least one voltage source connectable to the electronicdevices of the first cluster to provide a first test voltage to theelectronic devices of the first cluster in parallel and connectable tothe electronic devices of the second cluster to provide a first testvoltage to the electronic devices of the second cluster in parallel, atleast one current detector connectable to the devices of the firstcluster to measure a first test current from the devices of the firstcluster, the first test current from the devices of the first clusterthat is measured by the current detector being a total current of thedevices of the first cluster in parallel, and connectable to the devicesof the second cluster to measure a first test current from the devicesof the second cluster, the first test current that is measured by thecurrent detector from the devices of the second cluster being a totalcurrent of the devices of the second cluster in parallel, wherein thevoltage targeting system carries out a first comparison by comparing thefirst test current from the devices of the first cluster that ismeasured with a target current, a first voltage adjuster that adjuststhe first test voltage to a second test voltage for the first cluster inresponse to the first comparison so that the first test current from thedevices of the first cluster is adjusted to a second test current thatis closer to the target current, wherein the voltage targeting systemcarries out a second comparison by comparing the first test current fromthe devices of the second cluster that is measured with a targetcurrent; and a second voltage adjuster that adjusts the first testvoltage to a second test voltage for the second cluster in response tothe second comparison so that the first test current from the devices ofthe second cluster is adjusted closer to a second test current that iscloser to the target current.

The invention also provides a method of testing a plurality ofelectronic devices including holding the plurality of electronic devicesin at least first and second clusters, connecting at least one voltagesource to the electronic devices of the first cluster to provide a firsttest voltage to the electronic devices of the first cluster in paralleland connectable to the electronic devices of the second cluster toprovide a first test voltage to the electronic devices of the secondcluster in parallel, connecting the at least one voltage source to theelectronic devices of the second cluster to provide a first test voltageto the electronic devices of the second cluster in parallel, measuring,with at least one current detector, a first test current from thedevices of the second cluster, the first test current that is measuredby the current detector from the devices of the second cluster being atotal current of the devices of the second cluster in parallel,measuring, with the at least one current detector, a first test currentfrom the devices of the second cluster, the first test current that ismeasured by the current detector from the devices of the second clusterbeing a total current of the devices of the second cluster in parallel,carrying a first comparison out with a voltage targeting system bycomparing the first test current from the devices of the first clusterthat is measured with a target current, adjusting, with a first voltageadjuster, the first test voltage to a second test voltage for the firstcluster in response to the first comparison so that the first testcurrent from the devices of the second cluster is adjusted to a secondtest current that is closer to the target current, carrying a secondcomparison out with the voltage targeting system by comparing the firsttest current from the devices of the second cluster that is measuredwith a target current and adjusting, with a second voltage adjuster, thefirst test voltage to a second test voltage for the second cluster inresponse to the second comparison so that the first test current fromthe devices of the second cluster is adjusted closer to a second testcurrent that is closer to the target current.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is further described by way of examples with reference tothe accompanying drawings, wherein:

FIG. 1 is a cross-sectional side view of a tester apparatus having slotassemblies according to one embodiment of the invention;

FIG. 2 is a cross-sectional side view of the tester apparatus on line2-2 in FIG. 1;

FIG. 3 is a cross-sectional side view of the tester apparatus on line3-3 in FIG. 1;

FIG. 4 is a cross-sectional side view of the tester apparatus on line4-4 in FIGS. 2 and 3;

FIGS. 5A, 5B and 5C are perspective views of the tester apparatusillustrating insertion or removal of portable cartridges into or out ofan oven defined by a frame;

FIG. 6 is a time chart showing how one cartridge can be inserted andused for testing electronic devices of wafers and subsequent insertionof another cartridge;

FIG. 7 is a perspective view of the tester apparatus illustratinginsertion or removal of one slot assembly;

FIGS. 8A and 8B are cross-sectional side views illustrating the use of astand-off in the configuration of the cartridge described with respectto FIGS. 1-7;

FIGS. 9A, 9B and 10 are side views illustrating an apparatus that isused for insertion and removal of portable cartridges into and out ofthe oven;

FIG. 11 is a perspective view illustrating a cartridge according toanother embodiment of the invention;

FIG. 12 is a cross-sectional side view of a portion of the cartridge inFIG. 11;

FIG. 13 is a cross-sectional side view illustrating details of a portionof the view of FIG. 12;

FIGS. 14A and 14B are cross-sectional side views illustrating the use ofa stand-off in the configuration of FIGS. 11-13;

FIG. 15 illustrates components of the tester apparatus that are used tocontrol voltages to individual electronic devices;

FIG. 16 is a flow chart illustrating the operation of the components inFIG. 15;

FIG. 17 is a graph illustrating the voltage retargeting following theprocess of FIG. 16;

FIGS. 18A and 18B show histograms to illustrate static filtering that iscarried out in FIG. 16;

FIGS. 19A and 19B show histograms to illustrate outlier filtering thatis carried out in FIG. 16; and

FIGS. 20A and 20B show histograms to illustrate sample size filteringthat is carried out in FIG. 16.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 of the accompanying drawings illustrates a tester apparatus 10,according to an embodiment of the invention, that includes a tester 12,a frame 14, a power bus 16, first and second slot assemblies 18A and18B, a tester cable 20, a power cable 22, a cold liquid supply line 24A,a cold liquid return line 24B, a control liquid supply line 24C, acontrol liquid return line 24D, a vacuum line 24E, first and secondcartridges 28A and 28B, and first and second wafers 30A and 30B.

The slot assembly 18A includes a slot assembly body 32, a thermal chuck34, a temperature detector 36, a temperature modification device in theform of a heating resistor 38, a first slot assembly interface 40, and aplurality of second slot assembly interfaces, including a controlinterface 44, a power interface 46 and a cold liquid supply interface48A, a cold liquid return interface 48B, a control liquid supplyinterface 48C, a control liquid return interface 48D and a vacuuminterface 48E.

The first slot assembly interface 40 is located within the slot assemblybody 32 and is mounted to the slot assembly body 32. The secondinterfaces in the form of the control interface 44, the power interface46 and the interfaces 48A to 48E are mounted in a left wall of the slotassembly body 32.

The slot assembly 18A is insertable from left to right into and isremovable from right to left from the frame 14. The tester cable 20, thepower cable 22 and the lines 24A to 24E are manually connected to thecontrol interface 44, the power interface 46 and the interfaces 48A to48E respectively. Before removing the slot assembly 18A from the frame14, the tester cable 20, power cable 22 and the lines 24A to 24E arefirst manually disconnected from the control interface 44, powerinterface 46 and the interfaces 48A to 48E respectively.

The slot assembly 18A includes a motherboard 60 having test electronics,a plurality of channel module boards 62 having test electronics,flexible connecters 64, and a connection board 66. The control interface44 and the power interface 46 are connected to the motherboard 60 and athermal controller 50 is mounted to the motherboard 60. The channelmodule boards 62 are electrically connected to the motherboard 60. Theflexible connectors 64 connect the channel module boards 62 to theconnection board 66. Control functionality is provided throughelectrical conductors connecting the control interface 44 to themotherboard 60. Power is provided through the power interface 46 to themotherboard 60. Both power and control are provided from the motherboard60 through conductors to the channel module boards 62. The flexibleconnectors 64 provide conductors that connect the channel module boards62 to the connection board 66. The connection board 66 includes aconductor that connects the flexible connectors 64 to the first slotassembly interface 40. This first slot assembly interface 40 is thusconnected through various conductors to the control interface 44 andpower interface 46 so that power and control can be provided via thecontrol interface 44 and power interface 46 to the first slot assemblyinterface 40.

The second slot assembly 18B includes similar components to the firstslot assembly 18A and like reference numerals indicate like components.The second slot assembly 18B is inserted into the frame 14 and thecontrol interface 44, power interface 46 and interfaces 48A to 48E ofthe second slot assembly 18B are manually connected to a separate set ofconnecting components including a separate tester cable 20, a separatepower cable 22 and separate lines 24A to 24E, respectively.

The cartridge 28A includes a cartridge body formed by a thin chuck 72and a backing board 74. The wafer 30A has a plurality of microelectronicdevices formed therein. The wafer 30A is inserted into the cartridgebody between the thin chuck 72 and backing board 74. Cartridge contacts76 make contact with respective contacts (not shown) on the wafer 30A.The cartridge 28A further includes a cartridge interface 78 on thebacking board 74. Conductors in the backing board 74 connect thecartridge interface 78 to the cartridge contacts 76.

The cartridge 28A has a seal 77 connected between the backing board 74and the thin chuck 72. A vacuum is applied to an area defined by theseal 77, backing board 74 and the thin chuck 72. The vacuum keeps thecartridge 28A together and ensures proper contact between the cartridgecontacts 76 and the contacts on the wafer 30A.

The temperature detector 36 is in located in the thermal chuck 34 andtherefore close enough to the wafer 30A to detect a temperature of thewafer 30A or to within five degrees Celsius, preferably to within one ortwo degrees Celsius of the wafer 30A.

The slot assembly 18A further has a door 82 connected to the slotassembly body 32 by a hinge 84. When the door 82 is rotated into an openposition, the cartridge 28A can be inserted through a door opening 86into the slot assembly body 32. The cartridge 28A is then lowered ontothe thermal chuck 34 and the door 82 is closed. The thermal chuck 34 ismounted to the slot assembly body 32. The thermal chuck 34 thenessentially forms a holder having a testing station for a wafer.

The slot assembly 18A further has a seal 88 that is located between thethermal chuck 34 and the thin chuck 72. A vacuum is applied through thevacuum interface 48E and a vacuum line 90 to an area defined by the seal88, thermal chuck 34 and thin chuck 72. A good thermal connection isthereby provided between the thermal chuck 34 and the thin chuck 72.When heat is created by the heating resistor 38, the heat conductsthrough the thermal chuck 34 and the thin chuck 72 to reach the wafer30A. Heat conducts in an opposite direction when the thermal chuck 34 isat a lower temperature than the wafer 30A.

The cartridge interface 78 engages with the first slot assemblyinterface 40. Power and signals are provided via the first slot assemblyinterface 40, cartridge interface 78 and cartridge contacts 76 to thewafer 30A. A performance of devices within the wafer 30A is measuredthrough the cartridge contacts 76, cartridge interface 78 and first slotassembly interface 40.

The door 82 of the slot assembly 18B is shown in a closed position. Afront seal 100 is mounted on an upper surface of the slot assembly 18Aand seals with a lower surface of the slot assembly 18B. A front seal102 is mounted to an upper surface of the slot assembly 18B and sealswith a lower surface of the frame 14. A continuous sealed front wall 104is provided by the doors 82 of the slot assemblies 18A and 18B and thefront seals 100 and 102.

The slot assembly 18A further includes a thermal controller 50. Thetemperature detector 36 is connected through a temperature feedback line52 to the thermal controller 50. Power is provided through the powerinterface 46 and a power line 54 to the heating resistor 38 so that theheating resistor 38 heats up. The heating resistor 38 then heats thethermal chuck 34 and the wafer 30A on the thermal chuck 34. The heatingresistor 38 is controlled by the thermal controller 50 based on thetemperature detected by the temperature detector 36.

The thermal chuck 34 has a thermal fluid passage 224 formed therein. Thethermal fluid passage 224 holds a thermal fluid. The thermal fluid ispreferably a liquid as opposed to a gas because liquid is notcompressible and heat convects faster to or from a liquid. Differentthermal fluids are used for different applications with oil being usedfor applications where temperatures are the highest.

Control liquid supply and return lines 226 and 228 connect opposing endsof the thermal fluid passage 224 to the cold liquid supply and returninterfaces 48C and 48D, respectively. The heating resistor 38 serves asa heater that is mounted in a position to heat the thermal chuck 34,which heats the thermal fluid. By recirculating the thermal fluidthrough the thermal fluid passage 224, a more uniform distribution ofheat is provided by the thermal chuck 222 to the thermal chuck 34 andultimately to the wafer 30A. The temperature of the fluid can also becontrolled to add heat to the thermal chuck 34 or to cool the thermalchuck 34 down.

The tester apparatus 10 further includes a cooling system 240, atemperature control system 242 and a vacuum pump 244. The two coldliquid supply lines 24A that are connected to the first and second slotassemblies 18A and 18B are also connected through a manifold (not shown)to the cooling system 240. Additional manifolds connect the cold liquidreturn lines 24B to the cooling system 240, the control liquid supplylines 24C to the temperature control system 242, the control liquidreturn lines 24D to the temperature control system 242 and the vacuumlines 24E to the vacuum pump 244. Each slot assembly 18A or 18B has arespective cold plate 246 with a respective fluid passage 248. Thecooling system 240 circulates a fluid through the fluid passage 248 tocool the cold plate 246. The cold plate 246 then keeps the channelmodule boards 62 cool. The temperature control system 242 circulates afluid through the thermal fluid passage 224 to control a temperature ofthe thermal chuck 34 and transfer heat from or to the wafers 30A and30B. The vacuum pump 244 provides air at vacuum pressure to the vacuumline 90.

The slot assembly 18A includes a separator seal 108 mounted to an uppersurface the slot assembly body 32 above the internal wall 106 thereof.The separator seal 108 seals with a lower surface of the slot assembly18B. The slot assembly 18B has a separator seal 110 mounted to an uppersurface of the slot assembly body 32 thereof. The separator seal 108seals with a lower surface of the frame 14. A continuous sealedseparator wall 112 is provided by the internal walls 106 of the slotassemblies 18A and 18B and the separator seals 108 and 110.

FIG. 2 illustrates the tester apparatus 10 on 2-2 in FIG. 1. The frame14 defines a first closed loop air path 120. Air inlet and outletopenings (not shown) can be opened to change the first closed loop airpath 120 into an open air path wherein air at room temperature passesthrough the frame 14 without being recirculated. A closed loop path isparticularly useful in a clean room environment because it results inless particulate material being released into the air.

The tester apparatus 10 further includes a first fan 122, a first fanmotor 124 and a temperature modification device in the form of a watercooler 126.

The first fan 122 and first fan motor 124 are mounted in an upperportion of the first closed loop air path 120. The water cooler 126 ismounted to the frame 14 within an upper portion of the first closed loopair path 120.

The cartridges 28A and 28B are positioned with the slot assemblies 18Aand 18B and are within a lower half of the first closed loop air path120.

In use, current is provided to the first fan motor 124. The first fanmotor 124 rotates the first fan 122. The first fan 122 recirculates airin a clockwise direction through the first closed loop air path 120.

The water cooler 126 then cools the air in the first closed loop airpath 120. The air then flows through the slot assemblies 18A and 18Bover the cartridges 28A or 28B. The cartridges 28A or 28B are thencooled by the air through convection.

FIG. 3 shows the tester apparatus 10 on 3-3 in FIG. 1. The frame 14defines a second closed loop air path 150. The tester apparatus 10further includes a second fan 152, a second fan motor 154 and atemperature modification device in the form of a water cooler 156. Noelectric heater or damper is provided as in FIG. 2. Air inlet and outletopenings (not shown) can be opened to change the second closed loop airpath 150 into an open air path wherein air at room temperature passesthrough the frame 14 without being recirculated.

A closed loop path is particularly useful in a clean room environmentbecause it results in less particulate material being released into theair. The second fan 152 and second fan motor 154 are located in an upperportion of the second closed loop air path 150. The water cooler 156 islocated slightly downstream from the second fan 152 within the secondclosed loop air path 150. The motherboard 60 and channel module boards62 that form a part of the slot assemblies 18A and 18B are locatedwithin a lower half of the second closed loop air path 150.

In use, electric current is provided to the second fan motor 154, whichrotates the second fan 152. The second fan 152 then recirculates air ina clockwise direction through the second closed loop air path 150. Theair is cooled by the water cooler 156. The cooled air then passes overthe motherboard 60 and channel module boards 62 so that heat transfersfrom the motherboard 60 and channel module boards 62 to the air throughconvection.

Air recirculating through the first closed loop air path 120 in FIG. 2is kept separate from air in the second closed loop air path 150 in FIG.3 by the continuous sealed separator wall 112 shown in FIG. 1. Thecontinuous sealed front wall 104 shown in FIG. 1 prevents air fromescaping out of the first closed loop air path 120.

As shown in FIGS. 2 and 3, the same cooling system 240 that is used inFIG. 1 is also used to cool the water coolers 126. As shown in FIG. 4, aplenum 160 separates the first closed loop air path 120 from the secondclosed loop air path 150 in all areas except those provided by thecontinuous sealed separator wall 112. The frame 14 has left and rightwalls 162 and 164 that further define the closed loop air paths 120 and150.

FIGS. 5A, 5B and 5C illustrate how cartridges 30C, 30D and 30E can beinserted or be removed at any time while all other cartridges are beingused to test devices of wafers and may be in various states oftemperature ramps. FIG. 6 illustrates the concept in more detail. Attime T1 a first cartridge is inserted into the frame 14 while a secondcartridge is outside the frame 14. At T1 heating of the first cartridgeis initiated. Between T1 and T2 the temperature of the first cartridgeincreases from room temperature, i.e. about 22° C., to a testingtemperature that is 50° C. to 150° C. higher than room temperature atT2. At T2 power is applied to the first cartridge and the devices in thefirst cartridge are tested. At T3, a second cartridge is inserted intothe frame 14 and heating of the second cartridge is initiated. At T4,testing of the first cartridge is terminated. At T4, cooling of thefirst cartridge is also initiated. At T5, the second cartridge reachestesting temperature and power is provided to the second cartridge andthe wafer in the second cartridge is tested. At T6, the second cartridgereaches a temperature close to room temperature and is removed from theframe 14. A third cartridge can then be inserted in place of the firstcartridge. At T7, testing of the second cartridge is terminated andcooling thereof is initiated. At T8, the second cartridge has cooleddown to room temperature or close to room temperature and is removedfrom the frame 14.

Different tests can be conducted at different temperatures. By way ofexample, a cartridge may be inserted and a test be run at roomtemperature. Another test can be conducted during an upward ramp intemperature. A further test can be conducted at an elevated temperature.A further test can be conducted during a downward ramp in temperature.Two of these tests can be a single test that runs form one temperaturestage to the next.

As shown in FIG. 7, one slot assembly 18A can be removed or be insertedinto the frame 14. The slot assembly 18A can be inserted or be removedwhile the other slot assemblies within the frame 14 are used for testingdevices of wafers as described with reference to FIG. 6.

As shown in FIG. 8A, the backing board 74 includes a circuit board 500,a contactor 502, a plurality of pins 504, a securing ring 506, afastener 508, and a post 510.

The circuit board 500 is primarily made of an insulative material andhas a circuit (not shown) formed therein. Contacts 512 are formed on alower side 514 of the circuit board 500. A threaded opening 516 isformed into the lower side 514.

The contactor 502 has a plurality of pin openings 518, a post opening520 and a fastener opening 522 formed from an upper side 524 to a lowerside 526 therethrough. Each one of the pin openings 518 has a firstsection 528 and a second section 530. The first and second sections 528and 530 are both circular when viewed in plan view. The first section528 has a larger diameter than the second section 530. The largerdiameter of the first section 528 when compared to the diameter of thesecond section 530 results in the first section 528 being wider than thesecond section 530 when view in the cross-sectional side view of FIG.8A.

The post opening 520 has a first section 534 and a second section 536.The first section 534 and the second section 536 are both circular whenviewed in plan view. A diameter of the first section 534 is larger thana diameter of the second section 536. Because the diameter of the firstsection 534 is more than the diameter of the second section 536, thefirst section 534 is wider than the second section 536 when view in thecross-sectional side view of FIG. 8A. The first and second sections 534and 536 have vertical side walls. A horizontal landing 538 connects thevertical side walls of the first and second sections 534 and 536.

Each pin 504 includes an electrically conductive retainer portion 542, acoil spring 544 and first and second end pieces 546 and 548. The firstend piece 546 has a first inner portion 550 and a first tip 552. Thesecond end piece 548 has a second inner portion 554 and a second tip556. The coil spring 544 and the first and second inner portions 550 and554 are retained with the retainer portion 542 with the coil spring 544located between the first and second inner portions 550 and 554. Thefirst and second tips 552 and 556 protrude out of upper and lower ends,respectively, of the retainer portion 542.

An upper surface of the first tip 552 forms a terminal 560. A lower endof the second tip 556 forms a contact 562. The coil spring 544 and thefirst and second end pieces 546 and 548 are made of metal and,therefore, electrically conductive material. The coil spring 544 and thefirst and second end pieces 546 and 548 form a conductor that is capableof conducting current between the terminal 560 and the contact 562.

A respective pin is inserted through the upper side 524 into arespective pin opening 518. The second tip 556 is slightly smaller thanthe second section 530 so that it passes through the second section 530and protrudes from the lower side 526. The retainer portion 542 isslightly narrower than the first section 528, but is wider than thesecond section 530 to prevent the pin 504 from falling out of the lowerside 526. When the pin 504 is fully inserted into the pin opening 518,and before the contactor 502 is mounted to the circuit board 500, thefirst tip 552 still protrudes above the upper side 524 of the contactor502.

The post 510 has a stand-off 564, a force transfer potion 566 and aforce delivery portion 568. The post 510 is made out of a single pieceof metal or other material that is chosen because of its strength whencompared to the strength and brittleness of the ceramic material of thecontactor 502.

The post 510 is inserted through the upper side 524 into the postopening 520. The stand-off 564 and the force transfer portion 566 areslightly narrower than the second section 536. The force deliveryportion 568 is slightly narrower than the first section 534, but widerthan the second section 536. A lower surface 570 of the force deliveryportion 568 abuts against the landing 538. The post 510 is therebyprevented from falling out of the lower side 526.

The post 510 has a surface 572 that, when the post 510 is fully insertedas shown in FIG. 8A, is in a plane that is parallel and below a surfaceof the lower side 526. When the post 510 is fully inserted, the forcedelivery portion 568 has a surface 574 that is in the same plane as theupper side 524.

The circuit board 500 is positioned on top of the contactor 502. Eachone of the contacts 512 makes contact with a respective one of theterminals 560. Because the terminals 560 are in a plane above a plane ofthe upper side 524, the lower side 514 is initially spaced from theupper side 524.

The fastener 508 has a threaded shaft 578 and a head 580. The ring 506has a ring opening 582. The ring 506 is located on a lower surface 584of the contactor 502. The threaded shaft 578 is inserted from the bottomthrough the ring opening 582 and then through the fastener opening 522.The head 580 comes into contact with a lower surface of the ring 506.The head 580 is then turned so that thread on the threaded shaft 578screws into thread on the threaded opening 516. The threading actionmoves the circuit board 500 closer to the contactor 502 and the ring506. The lower side 514 eventually comes into contact with the upperside 524. The contacts 512 move the first end piece 546 downward intothe pin opening 518 until the terminals 560 are in the same plane as theupper side 524. The coil spring 544 compress, and therefore deformslightly to allow for relative movement of the first end piece 546relatively towards the second end piece 548.

The lower side 514 has a section that comes to a standstill against thesurface 574 forming part of the post 510. Because the post 510 abutsagainst the circuit board 500, the post 510 is in a position to transfera force through the surface 572 to the circuit board 500.

The first wafer 32A has a plurality of electronic devices formedtherein. Each electronic device has a plurality of terminals 588 at anupper surface 590 of the first wafer 32A. When bringing the backingboard 74 and the first wafer 32A together, the first wafer 32A isaligned with the backing board 74 to ensure that each one of theterminals 588 makes contact with a respective one of the contacts 562.

A vacuum pressure is created in an area between the upper surface 590and the lower side 526 while a pressure below a lower surface 592 of thethin chuck 72 and an upper surface 594 of the circuit board 500 remainat atmospheric pressure. The pressure differential creates equal andopposing forces F1 and F2 on the circuit board 500 and thin chuck 72.

As shown in FIG. 8B, the forces F1 and F2 move the backing board 74relatively towards the wafer 32A and the thin chuck 72. The coil springs544 compress more to allow for the second end piece 548 to move into thepin opening 518. Each coil spring 544 is deformed against a spring forcethereof, for example F3. The force F1 is, however, still more than thetotal of all the forces F3 added together. The upper surface 590eventually comes to rest against the surface 572 of the stand-off 564.Because the post 510 abuts against the circuit board 500, the stand-off564 prevents the upper surface 590 to move closer and into contact withthe lower side 526 of the contactor 502. The first wafer 32A transfers aforces F4 onto the stand-off 564. The force transfer portion 566transfers the force F4 through the second section 536 of the postopening 520. The force delivery portion 568 receives the force F4 fromthe force transfer portion 566 and delivers the force F4 via the surface574 to the circuit board 500.

It can thus be seen that the force F4 is not carried by contactor 502,thereby preventing stresses that could cause damage to the brittleceramic material of the contactor 502. Instead, the force F4 istransferred directly from an electronic device in the form of the firstwafer 32A through the post 510 onto the circuit board 500.

In the embodiment described in FIGS. 8A and 8B, the contactor 502 servesas a supporting board having a post opening 520 therethrough. Thecircuit board 500 serves as a backing structure, on a first side of thesupporting board, and including at least a circuit board having acontact 512. The pin 504 serves as a conductor having a contact 562 tomake contact with a terminal 588 on an electronic device positioned on asecond side of the supporting board opposing the first side of thesupporting board. The retainer portion 542 serves as a portion of theconductor that is held by the supporting board. The conductor furtherhas a terminal 560 that is connected to the contact 512 on the circuitboard 500. A spring in the form of the coil spring 544 is provided. Thethin chuck 72 serves as a force generation device on a side of theelectronic device in the form of the first wafer 32A opposing thesupporting board. The force generation device and the supporting boardare moveable relative to one another to move the electronic devicecloser to the supporting board and to deform the spring. The post 510has a stand-off 564 with a surface 572 in a plane spaced from a plane ofa surface of the supporting board to prevent movement of the electronicdevice closer to the supporting board, a force transfer portion 566extending from the stand-off 564 at least partially through the postopening 520 and a force delivery portion 568 extending from the forcetransfer portion 566, the force delivery portion 568 being held by thebacking structure.

FIG. 9A illustrates a portion of the tester apparatus 10 that is usedfor insertion of a cartridge into each slot assembly, for example intothe slot assembly 18A, and removal therefrom. The components of thetester apparatus 10 shown in FIG. 9A include a frame 300, a portion ofthe first slot assembly 18A, the first slot assembly interface 40, aholding structure 302, a horizontal transportation apparatus 304, avertical transportation apparatus 306, a beam spring 308, and a lockingmechanism 310.

The frame 300 includes first and second mounts 312 and 314 that arespaced from one another. The horizontal transportation apparatus 304 isa slide that is mounted between the first and second mounts 312 and 314.The holding structure 302 is mounted for sliding movement along thehorizontal transportation apparatus 304. Opposing ends of the beamspring 308 are mounted to the first and second mounts 312 and 314respectively.

The locking mechanism 310 includes a connection lever 316, a controllever 318 and a pressure lever 320. The control lever 318 is mounted tothe first mount 312 on a pivot connection 322. The verticaltransportation apparatus 306 is a rigid beam. A connection 324 connectscenter points of the vertical transportation apparatus 306 and the beamspring 308 to one another. The pressure lever 320 has a first link 326rotatably connected to the control lever 318 and a second link 328rotatably connected to an end of the vertical transportation apparatus306. In the unlocked configuration shown in FIG. 9A, a line 330 connectsthe pivot connection 322 with the second link 328 and the first link 326is to the left of the line 330.

In use, the first cartridge 28A is located on the holding structure 302.The first cartridge 28A is then moved together with the holdingstructure 302 from left to right into the first slot assembly 18A. Theplacement and movement of the first cartridge 28A may be manuallyexecuted or may be executed using a robot.

The holding structure 302 slides along the horizontal transportationapparatus 304. The connection lever 316 connects an end of the controllever 318 to the holding structure 302. When the holding structure 302moves in a horizontal direction along the horizontal transportationapparatus 304, the connection lever 316 rotates the control lever 318 ina counterclockwise direction about the pivot connection 322.

The first link 326 rotates together with the control lever 318 in acounterclockwise direction. The pressure lever 320 translates movementof the first link 326 to downwards movement of the second link 328. Atfirst, the downward movement is minimal, but when the first cartridge28A is fully inserted into the first slot assembly 18A, verticalmovement becomes more pronounced and the vertical transportationapparatus 306 engages the first cartridge 28A with the first slotassembly 18A. The horizontal transportation apparatus 304 is thusoperable to move the first cartridge 28A horizontally from a firstposition to a second position into the first slot assembly 18A and thevertical transportation apparatus 306 is operable to move the firstcartridge 28A and the first slot assembly 18A in a first verticaldirection relative to one another to engage the slot assembly interface40 with a cartridge interface on the first cartridge 28A.

The control lever 318 is shown in an unlocked position in FIG. 9A wherethe first link 326 is on a first side of the line 330 connecting thepivot connection 322 and the second link 328. The control lever 318rotates from the unlocked position shown in FIG. 9A through acompression position where the beam spring 308 is deformed by thevertical transportation apparatus 306 through the connection 324 bybending the beam spring 308 against a spring force thereof and the firstlink 326 is in line with the pivot connection 322 and the second link328. The control lever 318 continues to rotate from the compressedposition to a locked position as shown in FIGS. 9B and 10. In the lockedposition, the first link 326 is on the right of the line 330, andtherefore on a second side of the line 330 opposing the first side.Because the first link 326 has passed through the line 330, and the beamspring 308 has deformed against a spring force thereof, the firstcartridge 28A is locked in position against the slot assembly interface40.

The system can be unlocked by moving the holding structure 302 fromright to left. The control lever 318 rotates in a clockwise directionand the first link 326 moves right to left past the line 330. Thevertical transportation apparatus 306 moves in an upward direction, i.e.a second vertical direction opposing the first vertical direction, torelease the first cartridge 28A from the slot assembly interface 40.Further movement of the holding structure 302 along the horizontaltransportation apparatus 304 removes the first cartridge 28A from thefirst slot assembly 18A.

FIG. 11 illustrates a cartridge 340, according to a further embodimentof the invention, including a thermal subassembly 342, aboard-and-socket subassembly 344, and a plurality of lids 346.

FIG. 12 shows a portion of the thermal subassembly 342, a portion of theboard-and-socket subassembly 344 and one of the lids 346.

FIG. 13 shows detail A in FIG. 12, including a portion of the thermalsubassembly 342, a portion of the board-and-socket subassembly 344 and aportion of the lid 346. FIG. 13 further illustrates a first electronicdevice 348.

The thermal subassembly 342 includes a thin chuck 350, a first thermalanchor 352, and first thermal post 354. The thin chuck 350 has an uppersurface 356 with an opening 358 formed into the upper surface 356. Thefirst thermal anchor 352 and first thermal post 354 are machined out ofa single piece of metal. The first thermal anchor 352 and first thermalpost 354 both have circular cross-sections in respective planes parallelto an axis of the first thermal post 354 when viewed in plan view. Thecross-section of the first thermal anchor 352 is larger than thecross-section of the first thermal post 354.

The first thermal anchor 352 is inserted through the upper surface 356into the opening 358. The first thermal post 354 extends upwardly fromthe first thermal anchor 352. A majority of the first thermal post 354is located above the upper surface 356. The first thermal anchor 352 hasan upper end with a first thermal surface 360. The first thermal anchor352 is press fitted into the opening 358 up to a desired depth whereinthe first thermal surface 360 is at a desired distance from the uppersurface 356.

The first thermal post 354, first thermal anchor 352 and thin chuck 350are all made of metals and therefore are good thermal conductors. Thelarger cross-section of the first thermal anchor 352, when compared tothe cross-section of the first thermal post 354, results in more heattransfer from the first thermal anchor 352 to the thin chuck 350.

The board-and-socket subassembly 344 includes a circuit board 362, asocket 364, a first set of pins 366 for an electronic device, and afirst set of pins 368 for a detector. The pins 366 and 368 are pogo pinsthat contain springs and can compress against spring forces of thesprings.

The socket 364 includes a lower portion 370 and an upper portion 372.Each one of the pins 366 and 368 is retained within the socket 364between the lower portion 370 and the upper portion 372. The upperportion 372 has a first recessed formation 376 for holding the firstelectronic device 348. Each one of the pins 366 has a respective contact378 extending above a surface of the first recessed formation 376. Eachone of the pins 368 has a respective contact 380 that extends above anupper surface 382 of the upper portion 372.

The contacts 380 of the pins 368 are all in the same plane. The contacts378 of the pins 366 are all in the same plane. The plane of the contacts380 is parallel and above the plane of the contacts 378. The terminals392 of the pins 368 are all in the same plane as the terminals 392 ofthe pins 366.

The circuit board 362 has a circuit (not shown) formed therein. Contacts388 are formed within an upper surface 390 of the circuit board 362.

The socket 364 is positioned on the circuit board 362. The circuit board362 is thus located between the thin chuck 350 and the socket 364. Eachone of the pins 366 and 368 has a respective terminal 392 that initiallyextends below a lower surface 394 of the lower portion 370. A respectiveone of the terminals 392 makes contact with a respective one of thecontacts 388. The pins 366 and 368 are compressed against spring forcesthereof until the lower surface 394 makes contact with the upper surface390. The terminals 392 of the pins 366 and 368 move into the socket 364until they are in the same plane as the lower surface 394. The socket364 is then permanently mounted to the circuit board 362.

The socket 364 has a first socket thermal opening 398 formed from alower side to an upper side therethrough. The circuit board 362 has afirst circuit board thermal opening 400 formed from a lower side to anupper side therethrough. The first socket thermal opening 398 is alignedwith the first circuit board thermal opening 400. The thermalsubassembly 342 and the board-and-socket subassembly 344 are initiallydisconnected from one another as illustrated in FIG. 11. Theboard-and-socket subassembly 344 is then positioned over the thermalsubassembly 342. The first circuit board thermal opening 400 ispositioned over an upper end of the first thermal post 354. Theboard-and-socket subassembly 344 is then further lowered until the firstthermal post 354 passes through the first socket thermal opening 398. Alower surface 402 of the circuit board 362 comes to rest on the uppersurface 356 of the thin chuck 350. The first thermal post 354 fitsloosely within the first socket thermal opening 398 and the firstcircuit board thermal opening 400. The first thermal post 354 extendsabove the upper surface 356 because it is slightly longer than thecombined lengths of the first socket thermal opening 398 and the firstcircuit board thermal opening 400. The first thermal surface 360 is thuslocated slightly above an upper surface of the first recessed formation376. The contacts 378 are, at this stage, located in a plane above aplane of the first thermal surface 360.

The socket 364 is made of an electrically and thermally insulativematerial. The pins 366 and 368 provide electric conductors through thesocket 364. The circuit board 362 is also made of an electrically andthermally insulative material. The contacts 388 form part of an electriccircuit within the insulative material of the circuit board 362. Thefirst thermal post 354 provides a thermally conductive path between thefirst recessed formation 376 and the first thermal anchor 352 connectedto the thin chuck 350. The first thermal post 354 is electrically andthermally insulated from the electric conductors within the socket 364and the circuit board 362. Heat will conduct primarily through the firstthermal post 354 as opposed to the insulative material of the socket 364and the insulative material of the circuit board 362.

The lid 346 includes a circuit board 406 and a heat sink 408. Thecartridge 340 further has a first light detector 410, a first adjustablecomponent 412 and a first coil spring 414.

The circuit board 406 is made of an electrically and thermallyinsulative material. Electrically conductive terminals 416 are formed ona lower surface 418 of the circuit board 406. The terminals 416 formpart of a circuit (not shown) that is formed within the circuit board406.

The first light detector 410 is attached to an upper surface 420 of thecircuit board 406. The first light detector 410 is connected to theterminals 416 through the circuit in the circuit board 406. One of theterminals 416 may, for example, provide power to the first lightdetector 410. When light falls on the first light detector 410, thefirst light detector 410 coverts the energy of the light to outputelectric power. The other terminal 416 can serve as an output contactconnected to the first light detector 410 to measure the output electricpower.

The first adjustable component 412 has a pusher plate 422, sidewalls 424extending upwardly from the pusher plate 422, and a lip 426 extendingoutwardly from the sidewalls 424. The circuit board 406 has a firstopening 428 formed therein. The first adjustable component 412 isinserted into the first opening 428. The pusher plate 422 then extendsbelow the lower surface 418. The lip 426 comes to rest on the uppersurface 420. The first opening 428 is slightly larger than a widthbetween the sidewalls 424. The difference in widths allow the firstadjustable component 412 to rotate about a first axis 432 relative tothe circuit board 406 by a small amount of only a few degrees. Thedifference in widths also allows the first adjustable component 412 torotate clockwise and counter clockwise about a second axis 434, which isinto the paper and orthogonal to the first axis 432, relative to thecircuit board 406. Such orthogonal rotation allows for a small amount ofgimbaling of the first adjustable component 412 relative to the circuitboard 406.

The heat sink 408 has a first recess 436. The first coil spring 414 isinserted between the sidewalls 424. A lower end of the first coil spring414 rests on an upper surface 438 of the pusher plate 422. An upper endof the first coil spring 414 extends above the lip 426. The heat sink408 is located over the circuit board 406 with the upper end of thefirst coil spring 414 positioned within the first recess 436. A lowersurface 440 of the heat sink 408 is initially spaced from the uppersurface 420. The first coil spring 414 compresses and is thus deformedagainst a spring force thereof when the heat sink 408 is moved towardsthe circuit board 406. The lower surface 440 comes into contact with theupper surface 420. The heat sink 408 is then secured to the circuitboard 406 with fasteners (not shown). A small force created by the firstcoil spring 414 then biases the first adjustable component 412 is adirection out of the lower surface 418.

The pusher plate 422 has a first opening 442 therein. The heat sink 408defines a first cavity 444. A light absorbing coating is formed onsurfaces of the first cavity 444.

In use, the first electronic device 348 is inserted into the firstrecessed formation 376. Terminals 446 on a lower side of the firstelectronic device 348 make contact with the contacts 378. A lowersurface 448 of the first electronic device 348 is, at this stage, spacedfrom the first thermal surface 360.

The lid 346 is positioned over the board-and-socket subassembly 344. Thelid 346 is then moved towards the board-and-socket subassembly 344. Eachone of the terminals 416 comes into contact with a respective one of thecontacts 380. A lower surface 450 of the pusher plate 422 comes intocontact with an upper surface 452 of the first electronic device 348.The lower surface 448 of the first electronic device 348 is still spacedfrom the first thermal surface 360.

An operator manually presses, and thereby moves the lid 346 furthertowards the board-and-socket subassembly 344. Each one of the pins 366and 368 compresses against spring forces thereof, thus resilientlydepressing the contacts 378 and 380 against the spring forces of thesprings in the pins 366 and 368. The lower surface 448 of the firstelectronic device 348 comes into contact with the first thermal surface360.

If there is an angular misalignment between the first thermal surface360 and the lower surface 448 of the first electronic device 348, thefirst electronic device 348 is rotated by the first thermal surface 360until the lower surface 448 is in the same plane as the first thermalsurface 360. The rotation of the first adjustable component 412 relativeto the lid 346 allows for seating of the lower surface 448 of the firstelectronic device 348 against the first thermal surface 360. Goodthermal contact between the first thermal surface 360 and the lowersurface 448 is thereby ensured. The first coil spring 414 compresses toaccommodate a height of the first electronic device 348. Additionally,the first adjustable component 412 is rotatably mounted to the lid 346so that the first electronic device 348 can rotate the first adjustablecomponent 412 relative to the first thermal surface 360. The lid 346 isthen secured to the board-and-socket subassembly 344.

The socket 364 and the lid 346 jointly form an electronic device holderholding the first electronic device 348. A cartridge interface (notshown) on the circuit board 362 provides power and communication to andfrom the contacts 388. The pins 366 provide power and communication tothe first electronic device 348 via the terminals 446.

The first electronic device 348 may, for example, include a laser orother light transmitter. The first electronic device 348 may, forexample, have a laser transmitter in the upper surface 452 thereof. Whenpower and communication are provided to one of the contacts 378 servingas an input contact and one of the terminals 446 serving as an inputterminal, the laser transmitter of the first electronic device 348transmits laser light through the first opening 442 and through thefirst coil spring 414 and the sidewalls 424 into the first cavity 444.

A majority of the light is absorbed by the light absorbing material onthe surfaces of the first cavity 444, and thus converted to heat. Theheat conducts through the heat sink 408.

A small percentage of the light reflects off the surfaces of the firstcavity 444 and is detected by the first light detector 410. The firstlight detector 410 is powered through an electric conductor formed byone of the contacts 388, one of the pins 368, one of the terminals 416and a circuit formed within the circuit board 406. When the first lightdetector 410 detects the light, it converts the light to electric power.The magnitude of the electric power is in relation to the magnitude ofthe light detected by the light detector 410. The first light detector410 then provides the electric power to the circuit board 362 via aconductor that is formed jointly by a circuit in the circuit board 406,one of the terminals 416, one of the pins 368, one of the contacts 388and ultimately to the cartridge interface on the circuit board 362.

The circuit board 406 and the pins 368 provide a measurement channelconnecting the first light detector 410 to the circuit board 362, eventhough the first light detector 410 is on an opposite side of the firstelectronic device 348 than the circuit board 362. In a similar fashion,another type of detector, other than a light detector, may be used todetect features of an electronic device other than light transmitted bythe electronic device. It may, for example, be possible to detect acurrent on a terminal on an upper surface of an electronic device andcreate a similar measurement channel via a circuit board above theelectronic device and a pin located in a socket to a circuit board belowthe electronic device. In such an arrangement, a pin such as the pin 368can serve as a detector measurement pin held by a socket and formingpart of the measurement channel.

A temperature of the first electronic device 348 is controlled byconducting heat through the first thermal post 354. The first electronicdevice 348 may, for example, be heated or cooled through the firstthermal post 354. The first electronic device 348 can, for example, becooled by transferring heat from the first electronic device 348 throughthe first thermal post 354 and the first thermal anchor 352 to the thinchuck 350. The first electronic device 348 can be heated by transferringheat from the thin chuck 350 through the first thermal anchor 352 andthe first thermal post 354 to the first electronic device 348.

The thin chuck 350 is on a side of the first electronic device 348opposing the heat sink 408. It can thus be seen that the temperature ofthe first electronic device 348 can be controlled independently fromheat dissipation by the heat sink 408 due to laser light transmitted bythe first electronic device 348.

Referring again to FIG. 12, a plurality of electronic devices can betested using one socket 364 and one lid 346. The socket 364, forexample, includes a second thermal anchor 352A, a second thermal post354A, a second thermal surface 360A, a second set of pins 366A for asecond electronic device, a second set of pins 368A, a second recessedformation 376A for the second electronic device (not shown), a secondsocket thermal opening 398A, a second circuit board thermal opening400A, a second light detector 410A, a second adjustable component 412A,a second coil spring 414A, a second opening 428A, a second recess 436A,a second opening 442A, and a second cavity 444A. Like reference numeralsindicate like components and functioning.

Light transmitted by the first and second electronic devices can bedetected independently by the first and second light detectors 410 and410A. Heat, due to the light of the first and second electronic devices,is dissipated through the same heat sink 408. A plurality of fins 454are connected to the heat sink 408 and extend therefrom. The heatconducts to the fins 454 and then convects from the fins 454 to thesurrounding air. The fins 454 thus serve as a heat dissipation devicethermally connected to the heat sink 408 to remove the heat from theheat sink 408.

The temperatures of the first and second electronic devices are jointlycontrolled through the same thin chuck 350. Should the electronicdevices for example be cooled, heat conducts through the first andsecond thermal posts 354 and 354A to the first and second thermalanchors 352 and 352A, respectively, and then from the first and secondthermal anchors 352 and 352A to the thin chuck 350.

The first and second electronic devices are independently rotatable tomake contact with the first and second thermal surfaces 360 and 360A,respectively. Independent rotation of the first and second electronicdevices is permitted and controlled by the independent gimbaling of thefirst and second adjustable components 412 and 412A relative to the lid346.

Referring again to FIG. 11, sixteen sockets 364 are attached to thecircuit board 362. Each socket 364 has a respective lid 346. Each lid346 has a respective securing formation 460 and each socket 364 has arespective securing formation 462. The lid 346 is moved towards thesocket 364. The lid 346 is then pressed on to the socket 364 ashereinbefore described. The securing formations 460 and 462 then engagewith one another to secure the lid 346 to the socket 364 and maintainthermal and electrical integrity.

The thin chuck 350 has multiple thermal posts secured thereto in sixteengroups of sixteen. Each group of thermal posts is inserted through arespective one of the sockets 364. The electronic devices held by allsixteen sockets 364 are maintained at their temperatures using thesingle thin chuck 350.

A cartridge interface 464 is formed on a lower surface of the circuitboard 362. The cartridge interface 464 is connected through a circuit(not shown) to the contacts 388 shown in FIG. 13. The cartridgeinterface 464 is used to connect the cartridge 340 to an electric testeras hereinbefore described. The thin chuck 350 is thermally connected toa thermal chuck as hereinbefore described. The thermal chuck serves as atemperature modification device to control heat being transferred to orform the thin chuck 350.

Following testing of the electronic devices, the cartridge 340 isremoved from the system, the lids 346 are taken off and the electronicdevices are removed from the sockets 364.

The thermal post 354 also serves as a post that transfers a force in amanner similar to the embodiment described in FIGS. 8A and 8B. The lid346 serves as a force generation device. Some of the force created bythe lid 346 is balanced by forces created by the springs within the pins366 and 368. A remainder of the force that is not balanced by the pins366 and 368 is taken up by a stand-off of the post 354 having thesurface 360 to support the electronic device 348 and to prevent movementof the electronic device 348 closer to a base of the recessed formation376. A central portion of the post 354 serves as a force transferportion extending from the stand-off through the opening 398. Thecircuit board 362 and the thin chuck 350 jointly form a backingstructure. A lower portion of the post 354 delivers the force to thebacking structure in general. Specifically, the force is deliveredthrough the thermal anchor 352 to the thin chuck 350 forming part of thebacking structure. A press fit between the thermal anchor 352 and thethin chuck 350 is strong enough to remain in tact so that the force doesnot cause the thermal anchor 352 to move relative to thin chuck 350.

FIG. 14A illustrates the embodiment of FIGS. 11, 12 and 13, furtherillustrating details thereof including a fastener 600 and a post 602.

A post opening 604 and a fastener opening 606 are formed through thesocket 364. The post opening 520 has a first section 608 and a secondsection 610. The second section 610 is wider than the first section 608.The first section 608 may, for example, be formed though the upperportion 372 and the second section 610 may be formed through the lowerportion 370. A landing 612 connects the first section 608 to the secondsection 610.

The post 602 includes a stand-off 614, a force transfer portion 616 anda force delivery portion 618. The post 602 is inserted from the bottominto the post opening 604 until a surface 620 of the force deliveryportion 618 abuts against the landing 612. A threaded shaft 622 of thefastener 600 is inserted from the top through the fastener opening 606.A head 624 is then rotated so that thread on the threaded shaft 622screws into thread in a threaded opening 626 in the thin chuck 350.Because the thin chuck 350 is made out of metal it provides a goodanchor for the fastener 600. As the fastener 600 is further turned, thehead 624 moves closer to the circuit board 362. The springs of the pins366 compress slightly and a lower side 630 of the post 602 comes intocontact with the circuit board 362.

As shown in FIG. 14B, when the operator presses the lid 346 onto thesocket 364, the pusher plate 422 creates a force F1 that is equal andopposite to a reactive force F2 that is created in the thin chuck 350.The springs of the pins 366 compress against spring forces F3 thereof.The pusher plate 422 and the first electronic device 348 continue tomove closer to the socket 364 until the lower surface 448 of theelectronic device 348 comes into contact with a surface 632 of thestand-off 614. The surface 632 prevents further movement of theelectronic device 348 towards the socket 364.

The stand-off 614 receives a force F4 from the electronic device 348.The force transfer portion 616 transfers the force through the firstsection 608 of the post opening 604.

The force delivery portion 618 receives the force from the forcetransfer portion 616 and delivers the force to the circuit board 362.The circuit board 362 delivers the force to the thin chuck 350.

It can thus be seen that the material of the socket 364 is not exposedto the force F4 and damage to the socket 364 can thereby be eliminated.

The socket 364 provides a supporting board having a post opening 604therethrough. The circuit board 362 provides a backing structure, on afirst side of the supporting board, and has a contact 388. The pin 366forms a conductor having a contact 378 to make contact with a terminal446 on an electronic device 348 positioned on a side of the supportingboard opposing the first side of the supporting board. The conductor hasa portion held in the supporting board and a terminal 392 connected tothe contact 388 on the circuit board 362. A spring is provided withinthe pin 366. The pusher plate 422 forms a force generation device onside of the electronic device 348 opposing the supporting board. Theforce generation device and the supporting board are moveable relativeto one another to move the electronic device 348 closer to thesupporting board and deform the spring. The post 602 has a stand-off 614with a surface 632 in a plane spaced from a plane of a surface of thesupporting board to prevent movement of the electronic device 348 closerto the supporting board. The force transfer portion 616 extends from thestand-off 614 at least partially through the post opening 604. The forcedelivery portion 618 extends from the force transfer portion 616. Theforce delivery portion 618 is being held by the backing structure.

FIG. 15 illustrates further components of the tester apparatus 10 thatare used to accurately control voltages that are supplied to electronicdevices 634 that are being subjected to testing. The electronic devices634 may, for example, be located across the surface of a wafer 636 ormay be individual devices that are held within a layout of sockets.

Many semiconductor devices need a constant current supply versus aconstant voltage supply. An example of this is the burn-in (or aging) ofVertical Cavity Surface Emitting Lasers (VCSEL) wafers. The followingchallenges present themselves:

-   -   A VCSEL wafer has a very large number of devices in a very small        area. For example, assume a VCSEL wafer with 50,000 devices in a        3 inch circle.    -   The cost of 50,000 constant current sources would make the        system price too high for cost-effective burn-in.    -   Routing 50,000 power lines into a 3 inch circle would be        extremely difficult, if not impossible.

For purposes of further explanation, the following assumptions can bemade:

-   -   VCSELs are diodes, and as such, rarely have power to ground        shorts.    -   “Opens” can occur at a much higher frequency due to either        VSCELS being “open” or due to a bad contact to the wafer.    -   The internal resistance of a VCSEL is significant (about 100        ohms for a 10 mA VCSEL) and is VERY consistent (within 1%)        across a wafer.    -   It is very possible to build voltage sources which are very        accurate (within 1%.).    -   It is possible to measure the current fairly accurately for a        voltage source.    -   Most VCSEL wafers have a common cathode that limits the ability        to place VCSELs in series.    -   For illustration, assume:        -   VCSEL burn-in requires about 2.5 Volts and 10 mA.        -   Assume a system with 1024 power channels with up to 5 Volts            and 200 mA per channel.        -   Assume the system could provide constant current or constant            voltage per channel.        -   Assume the goal is to burn-in ¼ wafer (12,500 VCSELs) in a            single step.

The following is a list of existing burn-in circuit options:

-   -   (1) Individual Constant Current Sources. This gives precise,        measurable current to every VCSEL, but presents the following        problems:        -   Only about 2% of the wafer can be burned-in per step (1024            channels versus 50,000 devices).        -   The “cost” per VCSEL is 1 channel. Even if additional            channels could be added, the cost would remain 1 channel per            VCSEL.        -   Even if the system could be expanded to 12,500 channels (the            minimum number of channels required to burn-in ¼ of the            wafer) it would be impossible or cost prohibitive to route            12,500 power channels into the 3 inch wafer area.    -   (2) Series wiring. This would require placing about 13 VCSELs in        series and driving with a constant current source, but presents        the following problems:        -   Since VCSELs all have a common cathode, it is not possible            to wire a wafer of VCSELs in series.        -   This would require a current source of 10 mA and over 30            Volts. Protecting such a high voltage against current surges            is very difficult.    -   (3) Parallel wiring with current source. Drive about 13 VCSELs        in parallel with a constant current source. This would require a        2.5 Volt, 130 mA current source. This system presents the        following problems:        -   For every VCSEL that has an “open” or bad probe contact, the            extra current gets distributed among the rest of the VCSELs            in the group. Thus, each VCSEL would get about an extra 8%            current (130 mA/12 VCSELs) for every bad VCSEL in a group.        -   If the voltage does not shift significantly due to the open            VCSEL, it will not be known that the other 12 VCSELs            received the wrong burn-in current and thus bad devices            might escape detection.    -   (4) Parallel wiring with a voltage source. Such a system would        drive 13 VCSELs in parallel with a constant voltage source. The        voltage source is chosen to be the required voltage for all 13        VCSELs to receive 10 mA of current. This system presents the        following problems:        -   If a VCSEL is open, then the total current in the group will            be a little less. For every open VCSEL, the group current            will be 10 mA lower (for example, 140 mA for the group            versus 150 mA.) The rest of VCSELs in the group will still            get 10 mA.        -   The stability of the current per VCSEL in the group is very            good. In the worst case it is the accuracy of the voltage            supply (<1%) and the consistency of the internal resistance            of a good VCSEL (<1% across a wafer.) Thus, the current            through each VCSEL will be consistent to within 2% across            the wafer using a parallel voltage source.        -   If a VCSEL were to have a short (highly unlikely), then the            over-current protection on the power channel would shut down            that power channel, leaving the other channels still            operating.

Existing solutions can thus be summarized as follows:

-   -   Circuit 1 is the ideal circuit, but cost and technical issues        exclude it.    -   Circuit 2 is not possible on a common cathode VCSEL wafer.    -   Circuit 3 gives very poor results in the most common failure        mode, “open” devices.    -   Circuit 4 gives very good results in almost all cases and is        very cost-effective.

Circuit 4 (parallel wiring with a voltage source) presents the followingproblems:

-   -   The correct voltage needs to be chosen for the voltage source        for the VCSELs to receive the proper current.    -   The proper voltage is a function of several factors:        -   VCSEL construction. The design of the VCSEL determines the            voltage at the desired current.        -   VCSEL fabrication process variations from wafer to wafer.            Due to process variation, the voltage at a given current can            vary from wafer to wafer.        -   VCSEL fabrication process variations across a wafer. The            voltage at a given current can vary from devices near the            wafer edge from those at wafer center.        -   The voltage at a specific current varies with temperature.            Not only the heat being added for burn-in, but also the            device's own internal heating can vary the voltage at a            given current.        -   As a VCSEL ages, its voltage/current relationship shifts.            Thus even if the voltage was correct at the start of a            burn-in cycle, the proper voltage at the end will likely be            lower.

FIG. 15 only shows the electronic devices 634 of a first group (Group 1)of clusters (Clusters 1 to 4) of electronic devices 634 located in aregion near an edge of the wafer 636. It should be understood that thereare 16 groups (Groups 1 to 4) of clusters and each group has 64 clustersand each cluster has twelve electronic devices 634.

The electronic devices 634 of the first cluster (Cluster 1) areconnected to one another in parallel, either through conductors formingpart of the wafer 636 or by an external device forming part of thetester apparatus 10. Further clusters (Clusters 2 to 4) of electronicdevices (not shown) are located in further regions of the first group(Group 1). Each cluster has a respective set of twelve electronicdevices that are connected to one another in parallel. The electronicdevices forming one cluster are not electrically connected to theelectronic devices forming part of any other cluster.

The tester apparatus 10 includes a cluster selector switch 638, acurrent detector 640, a static filter 642, an outlier filter 644, asample size filter 646, a voltage targeting system 648, a voltage source650, and first and second voltage adjusters 652 and 654.

Each cluster provides a separate current output to the cluster selectorswitch 638. The cluster selector switch 638 is adjustable to selectablyconnect the current detector 640 to a respective one of the currentoutputs 660. Current from a respective current output 660 passes throughthe current detector 640 to ground 662.

The cluster selector switch 638 is typically operated to connect eachone of the current outputs 660 to the current detector 640. The currentdetector 640 thus detects currents from each one of the clusters.

The current detector 640 provides an output to the static filter 642.The static filter 642 is adapted to remove a current reading for arespective cluster that is above or below set limits. The static filter642 typically processes data for all of the clusters at the same time toremove data for clusters that have current readings that are above orbelow set limits.

The static filter 642 passes data to the outlier filter 644. The outlierfilter 644 removes a current reading for a respective cluster that istoo far or below a median for a group of the clusters. The outlierfilter 644 passes data on to the sample size filter 646. The sample sizefilter 646 stops computing a mean for current readings for clusters thatinclude the cluster if the number of channels (devices) for the clusteris too small.

The voltage source 650 is connected through the voltage adjuster 652 toinput voltage terminals of the electronic devices 634 of the firstgroup. The voltage source 650 is further connected through the voltageadjuster 654 to input terminals of the electronic devices of the secondgroup. Similarly, the voltage source 650 is connected through furthervoltage adjusters (not shown) to the electronic devices of further onesof the groups.

The voltage targeting system 648 receives data from the sample sizefilter 646 and adjusts the voltage adjusters 652 and 654 based on thedata.

FIG. 16 illustrates a method of testing the plurality of electronicdevices 634 using the components of the tester apparatus 10 in FIG. 15.

At 700, the plurality of electronic devices are held in clusters asdescribed above. At 702, the voltage source 650 is connected to theelectronic devices 634 of the first cluster. As described above, thevoltage source 650 is connected to the electronic devices 634 to providea voltage to the electronic devices 634 of the first cluster inparallel. At 704, the voltage source 650 is connected through thevoltage adjuster 652 to the electronic devices of the second cluster toprovide a voltage to the electronic devices of the second cluster inparallel. Similarly, at 706, the voltage source 650 is connected throughthe voltage adjuster 652 to the electronic devices of the third clusterto provide a voltage to the electronic devices of the third cluster inparallel. The voltage source 650 may similarly be connected through thevoltage adjuster 652 to further clusters of the electronic devices toprovide a voltage to the electronic devices of each cluster in parallel.

Referring to FIG. 17, a slope of a curve is calculated by firstdetermining voltage guesses “A” and “B”. Steps 708 to 724 in FIG. 16correspond to the calculation of the slope.

At 708, a first initial voltage guess “V_(A)” is made and a resultingfirst initial current “I_(A)” is measured using the current detector 640in FIG. 15. The voltage source 650 in FIG. 15 provides the first initialvoltage guess for electronic devices 634 of the first cluster inparallel. The second, third and further clusters receive similartreatment as the first cluster. For example, the voltage source 650provides a first initial voltage guess for the electronic devices of thesecond cluster in parallel.

The cluster selector switch 638 in FIG. 15 is sequentially switchedthrough the current outputs 660 from the respective clusters of thefirst group. When the cluster selector switch 638 is connected to thecurrent output 660 of the first cluster, the current detector 640measures the first initial current from the electronic devices 634 ofthe first cluster. The first initial current from the electronic devices634 of the first cluster that is measured by the current detector 640 isa total current of the electronic devices 634 of the first cluster inparallel. When the cluster selector switch 638 is switched to thecurrent output 660 of the second cluster, the second cluster receivessimilar treatment as the first cluster, as indicated by the dashed linebetween 704 and 710 in FIG. 16. Similarly, by continuing to switch thecluster selector switch 638 to subsequent current outputs 660, thecurrent detector 640 measures a first initial current for the electronicdevices of each respective cluster.

The current detector 640 provides the current measurements to the staticfilter 642 in FIG. 15. As more clearly seen in FIG. 16, multi-stagefiltering 710 is carried out, which includes static filtering 712,outlier filtering 714, and sample size filtering 716. As shown in FIG.16, the static filter 642 of FIG. 15 carries out static filtering at712.

FIGS. 18A and 18B illustrate static filtering in more detail. Individualcurrents from the first and second groups are shown. Static filteringremoves current readings above and below set limits; e.g., below 2 andabove 6. Static filtering may for example remove a first initial currentreading for a respective cluster in a respective group that is above andbelow set limits. Any given cluster might have an “open” VCSEL and thusnot return a correct total current for all of the VCSELs. Current limitscan be used to determine if any given reading appears to be correct.

Following static filtering, the data is processed at 714 in FIG. 16 tocarry out outlier filtering with the outlier filter 644 in FIG. 15.FIGS. 19A and 19B illustrate outlier filtering in more detail. Outlierfiltering removes data too far above and below the median of the data;e.g., +/−20%. Outlier filtering may for example remove a first initialcurrent reading for a respective cluster that is too far above or belowa median for the group. Additional filtering can use statistical methodsto determine if a first initial current reading of a given channel isabnormal.

Following outlier filtering, the data is processed at 716 in FIG. 16 tocarry out sample size filtering with the sample size filter 646 in FIG.15. Sample size filtering is illustrated in FIGS. 20A and 20B. Samplesize filtering stops computing a mean of the first initial currentreadings of groups if the number of remaining clusters is too small,e.g., <10. If any group has too few clusters left for propercomputations, the mean computation of surrounding groups can be used.Two sample groups are included to show how the filtering would progress.After the outlier filtering, the second group has too few clusters leftto give a reliable computation for the voltage. In that case, theaverage of the other group is used.

At 720 in FIG. 16, a second voltage guess “V_(B)” is made and appliedand a resulting second initial current “I_(B)” is measured. The secondinitial voltage guess is applied in a manner that is the same as thefirst initial voltage guess at 708. A second initial current is measuredfor each one of the clusters.

At 722, multi-stage filtering is carried out on the data that includesthe second initial currents from the clusters. The multi-stage filteringcarried out at 722 is the same as the multi-stage filtering carried outat 710.

FIG. 17 shows the locations of the first and second initial currentsafter they pass through the multi-stage filtering at 710 and 722.Current measurements are shown on the Y axis and Time is shown on the Xaxis. A current slope is given by the equation:

Slope=(V _(B) −V _(A))/(I _(B) −I _(A))

The slope is thus calculated by dividing the difference between thesecond and first initial voltages for the electronic devices of thefirst group by a difference between the second and first initialcurrents for the electronic devices of the first group.

Steps 708, 712 and 724 that are describe above are executed by thevoltage targeting system 648 in FIG. 15. The voltage targeting system648 controls the voltage adjuster 652 to provide the voltages to theelectronic devices of the respective clusters. The voltage targetingsystem 648 then stores the calculated slope in memory.

Following the computation of the slope at 724 in FIG. 17 and storing ofthe slope, the voltage targeting system 648 can use the slope to set andretarget test voltages that are applied to each cluster of electronicdevices 634. The setting and retargeting of the test voltages isillustrated by steps 726 to 736 in FIG. 16.

At 726, a guess is made for a first test voltage (V_(G)) and a resultingfirst test current (I_(G)) is measured. It should be understood from thedescription above and FIG. 15 that the voltage targeting system 648 setsthe voltage adjuster 652 so that the voltage source 650 applies thefirst test voltage to the electronic devices 634 of the first cluster inparallel. It should further be understood that the first test currentfrom the electronic devices 634 of the first cluster that is measured bythe current detector 640 is a total current of the electronic device 634of the first cluster in parallel.

The second and third clusters of the first group receive similartreatment. Each additional cluster thus has a respective first testvoltage that is applied to the devices of the cluster and has a firsttest current that is measured from the devices.

Following the measurement of the first test currents from the clusters,the data of the first test currents again proceed through multi-stagefiltering 730. The multi-stage filtering 730 is carried out on the firsttest currents in a manner similar to the multi-stage filtering 710 thatwas carried out on the first initial currents from the clusters and themulti-stage filtering 722 that was carried out on the second initialcurrents from the clusters of the first group.

At 732, a first comparison is made between the first test current and atarget current. Specifically, the measured first test current issubtracted from the target current. The difference is recorded as theamount of current error that has to be corrected for. FIG. 17 shows thefirst initial current as a result of the first initial guess (“G”), thetarget current (I_(T)) and the current error (I_(T)−I_(G)).

At 734 in FIG. 16, retargeting is carried out. A second test voltage iscomputed and the first test voltage is adjusted to the second testvoltage. As shown in FIG. 17, the second test voltage is calculatedaccording to the formula:

V _(G)+(I _(T) −I _(G))*Slope

The first comparison at 732 thus forms a basis for the voltageadjustment at 734.

736 in FIG. 16 indicates that the process starting at 726 can berepeated by using the retargeted voltage as the first test voltage andthen measuring a test current and calculating a retargeted voltage.

The dashed lined from 702 to 706 in FIG. 16 indicate that the second andthird groups of clusters receive similar treatment to the first group ofclusters. In the given example, the voltage source 650 provides avoltage through the voltage adjuster 654 to the electronic devices ofthe second group. The voltages applied to the electronic devices of thefirst and second groups can be independently controlled in the mannerdescribed above. In a similar manner, a separate voltage adjusterprovides a voltage to the electronic devices of a separate group.Although only a single current detector 640 is shown, it should beunderstood that multiple current detectors can be included in the systemto detect currents from one or more clusters in one or more groups.

As noted above, parallel wiring with a voltage source has distincteconomic advantages. In addition, the voltage retargeting process, asdescribed above, ensures that accurate voltages are applied to devicesthat are connected using parallel wiring with a voltage source to ensurethat the devices receive the correct currents according to theirspecification.

The clusters can be chosen to match wafer processing (or other) factorsthat might affect the voltage/current relationship.

-   -   It is not uncommon that devices near the edge of the wafer will        have characteristics different from devices from near the center        of the wafer.    -   Clusters can be chosen such that edge device are analyzed with        other edge devices and center devices are analyzed with other        center devices.

The retargeting process is highly convergent and not sensitive to slighterrors.

-   -   For example, assume the initial voltage/current computation was        performed poorly and the resulting slope was off by 20%.    -   Assume for the first retargeting step that the computed voltage        was wrong by 50% (i.e., the current was wrong by 50%.)    -   The first retargeting would attempt to correct the 50% current        error with a slope that has a 20% error. The net correct would        then be wrong by 10% (50% * 20%).    -   The next retargeting step would then correct this 10% error and        again miscompute by 20%. This correction would wrong by only 2%        (10%*20%).    -   Thus after only 2 retargeting steps, with a starting error of        50% and a slope error of 20%, the resulting current is now        within 2%.    -   This illustrates the rapid convergence this retargeting        algorithm. More typically, the slope will be computed within        about 5% and the initial current will be within 20%. Then only a        single step is required to be within 1% of the correct current.

While certain exemplary embodiments have been described and shown in theaccompanying drawings, it is to be understood that such embodiments aremerely illustrative and not restrictive of the current invention, andthat this invention is not restricted to the specific constructions andarrangements shown and described since modifications may occur to thoseordinarily skilled in the art.

1-27. (canceled)
 28. A cartridge comprising: a socket of insulativematerial and having upper and lower sides, a first formation on theupper side to hold a first electronic device, and a second formation onthe upper side to hold a second electronic device; a lid; a first pusherplate rotatably mounted to the lid; a second pusher plate rotatablymounted to the lid, the lid being locatable over the socket and movabletowards the socket, the rotatable mounting of the first pusher plateallowing for the first electronic device to rotate the first pusherplate relative to the lid and the rotatable mounting of the secondpusher plate allowing the second electronic device to rotate the secondpusher plate independently from the first pusher plate relative to thelid; a first set of contacts held in the socket to connect to the firstelectronic device; a first set of terminals connected to the first setof contacts; a second set of contacts held in the socket to connect tothe second electronic device; and a second set of terminals connected tothe second set of contacts.
 29. The cartridge of claim 28, wherein thefirst pusher plate is rotatable about first and second orthogonal axesrelative to the lid and the second pusher plate is rotatable about firstand second orthogonal axes relative to the lid.
 30. The cartridge ofclaim 28, further comprising: a first thermal surface within the firstformation, wherein the rotation of the first pusher plate relative tothe lid allows for seating of a lower surface of the first electronicdevice against the first thermal surface; and a second thermal surfacewithin the second formation, wherein the rotation of the second pusherplate relative to the lid allows for seating of a lower surface of thesecond electronic device against the second thermal surface.
 31. Thecartridge of claim 30, wherein the first set of contacts are resilientlydepressible to bring the first electronic device into contact with thefirst thermal surface and the second set of contacts are resilientlydepressible to bring the second electronic device into contact with thesecond thermal surface.
 32. The cartridge of claim 28, furthercomprising: a first spring connected between the lid and the firstpusher plate, the first pusher plate being linearly movable by the firstelectronic device relative to the lid to cause deformation of the firstspring; and a second spring connected between the lid and the secondpusher plate, the second pusher plate being lineally movable by thesecond electronic device relative to the lid to cause deformation of thesecond spring.
 33. The cartridge of claim 32, wherein the first pusherplate has a first pusher plate lip and the lid has a first lid ledge,wherein the first pusher plate lip rests on the first lid ledge toprevent the first spring from moving the first pusher plate out of thelid and the second pusher plate has a second pusher plate lip and thelid has a second lid ledge, wherein the second pusher plate lip rests onthe second lid ledge to prevent the second spring from moving the secondpusher plate out of the lid.
 34. The cartridge of claim 28, furthercomprising: a securing formation on the lid; and a securing formation onthe socket, the securing formation on being engageable with one anotherto secure the lid to the socket after moving the lid towards the socket.35. The cartridge of claim 28, wherein the socket has a third formationon the upper side to hold a third device, further comprising: a thirdpusher plate rotatably mounted to the lid, the rotatable mounting of thethird pusher plate allowing the third device to rotate the third pusherplate independently from the second pusher plate relative to the lid; athird set of terminals held in the socket to connect to the thirddevice; and a third set of contacts connected to the third set ofterminals.
 36. A method of testing one or more electronic devicescomprising: releasably holding a first electronic device in a firstformation on an upper side of a socket of insulative material;releasably holding a second electronic device in a second formation onan upper side of a socket; locating a lid over the socket, the lidhaving a first pusher plate rotatably mounted to the lid and a secondpusher plate rotatably mounted to the lid; moving the lid towards thesocket, the rotatable mounting of the first pusher plate allowing forthe first electronic device to rotate the first pusher plate relative tothe lid and the rotatable mounting of the second pusher plate allowingthe second electronic device to rotate the second pusher plateindependently from the first pusher plate relative to the lid; andconnecting the first and second electronic devices to an electric testerthrough an interface connected to the socket. 37-96. (canceled)